Patients meeting DSM-III-R criteria for panic disorder and nervous pointer dogs, an animal model of panic disorder, are evaluated using chemical model strategies, neuroendocrine challenge techniques, and physiological and biochemical methodologies. Particular attention is given to the role of the noradrenergic, dopaminergic, serotonergic, adenosinergic, and cholinergic neurotransmitter or neuromodulatory systems in the pathogenesis of abnormal fear behaviors and regulation of hypothalamic-pituitary function. Patients with panic disorder were found to have diurnal changes in ratings of generalized anxiety, phobic anxiety and frequency of panic attacks and increased anxiogenic responses to m-CPP and pentagastrin. Both panic disorder humans and nervous pointer dogs have disturbances in hypothalamic-growth hormone function; in nervous dogs, this abnormality is associated with decreased levels of IGF-I in the plasma.